This invention relates to a mechanism for closing a microwave oven door and more particularly to a mechanism which allows a microwave oven door to be released from an engaged condition with a shorter stroke by reduced force.
A previously considered mechanism for closing a door and a microwave oven incorporating such a mechanism are respectively shown in FIGS. 4 and 5. A door 3 is provided for opening and closing an oven chamber 2 in a frontal part of the housing 1. Numeral 4 in FIG. 4 indicates a front panel of the oven chamber 2 provided with two latch hooks 5 (only one of them shown) to keep the door 3 in the closed condition. The door 3 is correspondingly provided with two elongated latch heads 7 such that they will pass through two openings 6 on the front surface of the housing 1 when the door 3 is closed. Each latch head 7 has a hook-shaped front end 9 so as to be engageable with corresponding one of the latch hooks 5. A holder 8 is provided outside of the oven chamber 2 but inside the housing 1 for mounting a switch 11 with a plunger 10 such that the hook-shaped front end 9 of the latch head 7 presses the plunger 10 to cause the output of a start signal when the door 3 is closed and the latch head 7 becomes engaged with the latch hook 5. The plunger 10 is retractably protruding and generally assumes the protruding position by biasing means (not shown).
The door 3 is released from the closed condition, that is, the engaged relationship between the latch head 7 and the latch hook 5 is terminated if an OPEN button 12 provided on an external surface of the housing 1 to operate a door releasing mechanism (not shown), thereby lifting the hook-shaped front part 9 of the latch head 7 upward. There is also another biasing spring (not shown) applying a downward biasing force on the front end 9 of the latch head 7 so that the plunger 10 will keep the switch in the ON position against the biasing force of the aforementioned biasing means on the plunger 10 when the latch head 7 is engaged with the latch hook 5.
With a mechanism described above, a fairly large force is required to press the hook-shaped front part 9 of the latch head 7 downward in order to keep the plunger 10 of the switch 11 pressed until the switch 11 is in the ON condition. Therefore, a correspondingly large force is required to lift the front part 9 of the latch head 7 to release the engagement of the latch head 7 with the latch 5. In other words, the latch 5 is heavy to operate. If the mechanism is so designed that the operation of the latch head 7 can be completed quickly by reducing the distance with which the latch head 7 must be lifted (or the so-called "stroke"), the end of the hook-shaped front part 9 of the latch head 7 comes to rub against the upper surface of the latch 5 and this tends to cause injury to the latch head 7 and the latch hook 5. On the other hand, the operation becomes troublesome to the user if the large stroke is required to release the engagement of the door.